1. Field of the Invention
The present invention relates to a spread illuminating apparatus used as an illumination unit of a liquid crystal display device or the like.
2. Description of the Related Art
Liquid crystal display devices are now regularly used as display devices of electronic apparatuses such as personal computers and mobile telephones. Liquid crystal is not a self-luminous display element, and thus an illumination unit for irradiating light onto the liquid crystal panel is required. As such an illumination unit for a liquid crystal display device, a spread illuminating apparatus including a light guide plate and a light source disposed to the side of the light guide plate as the main constituent elements is widely used in combination with a liquid crystal display device because such a spread illuminating apparatus has an advantage of being easy to make thin. Further, due to recent enhancements in the performance of white light-emitting diodes (LEDs), spread illuminating apparatuses utilizing white LEDs as a light source are now common in order to achieve further reductions in the size, thickness, and power consumption of spread illuminating apparatuses.
An example of such a spread illuminating apparatus will now be explained while referring to the constitution (FIG. 9) of a spread illuminating apparatus 10 according to an embodiment of the present invention to be explained later.
The spread illuminating apparatus 10 has a basic constitution in which a light guide plate 12 and LEDs 14 disposed opposing an incident light surface 12c of the light guide plate 12 are accommodated in a housing frame 16. Since the LEDs 14 are point light sources, when light emitted from the LEDs 14 enters into the light guide plate 12 from the incident light surface 12c, there are cases in which brightness unevenness referred to as brightness spots or hot spots may occur. Such brightness unevenness may impair the uniformity of the brightness at a light emitting surface 12a, which is one of the principal surfaces of the light guide plate 12. Therefore, the occurrence of such brightness unevenness must constantly be suppressed in order to secure high quality visibility of the object to be illuminated such as a liquid crystal display device or the like. Thus, technology for preventing the occurrence of brightness unevenness is being developed (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2013-26138).